Methods for providing prepaid telephony service via an internet protocol network system

ABSTRACT

Methods are disclosed for providing prepaid telephony service via an Internet protocol (IP) network system. A first method provides controlling at least one media agent or call routing station/switch of an IP network system for allowing and/or blocking call media streams from traversing through the media agent. A second method provides directing all signaling messages transmitted by a signaling agent or station and all media packets transmitting voice and data communications through at least one common device within the IP network system. The methods further provide for continuously monitoring a subscriber&#39;s account balance and terminating the prepaid telephony service if the account balance is less than a predetermined amount.

RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 10/230,787, filed Aug. 28, 2002 now U.S. Pat. No. 7,010,103,which is a continuation of U.S. application Ser. No. 09/436,294, filedNov. 8, 1999, issued as U.S. Pat. No. 6,480,588.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to telecommunications systems,and more specifically is directed toward methods of providing prepaidtelephony service via an Internet protocol (IP) network system.

2. Description of the Related Art

Prepaid telephony service is a very popular service in the existingPublic Switched Telephone Network (PSTN). For example, prepaid callingcards are typically used by PSTN subscribers to place calls. Typically,a user or subscriber of a prepaid calling card initiates a phone call bycalling a signaling agent, such as a communications station or server,via a toll-free number (800/888) provided on the prepaid calling card.The subscriber is then prompted to enter his home telephone number andan identification number (PIN) also provided on the prepaid calling cardusing a telephone keypad.

The signaling agent then proceeds to perform validation procedures todetermine if the home telephone number matches the identification numberusing a look-up table stored within a database or if the identificationnumber is valid. If the two numbers match or if the identificationnumber is valid, then the signaling agent performs database queries todetermine if the subscriber's account balance is more than apredetermined amount. If the account balance is more than thepredetermined amount, then the signaling agent informs the subscriber ofthe length of calling time available and indicates to the subscriber toenter a number to be dialed. The signaling agent then proceeds to placethe call by transmitting signaling messages to appropriatecommunications devices along a media path flow, i.e., the path throughwhich call media streams are routed through the PSTN. If the accountbalance is less than the predetermined amount, then the signaling agentinforms the subscriber that a call cannot be placed.

During the duration of the call, the signaling agent monitors thesubscriber's account balance. If the account balance falls below thepredetermined amount, the signaling agent transmits a message to thesubscriber via the same media path flow as the path of the call mediastreams indicating to the subscriber the amount of available time. Afterthe subscriber's account balance has been depleted, the signaling agenttears down the PSTN call by blocking the media path flow as describedbelow.

In the PSTN, the call is torn down by the signaling agent transmitting a“switch-off” signaling message to a media agent or a routing stationalong the media path flow through which the call media streams arerouted through. The “switch-off” signaling message disables the mediaagent to prevent the call media streams from being transmitted furtheralong the media path flow. Hence, the PSTN call is torn down.

It is inconsequential if the signaling agent is or is not located alongthe media path flow, since in the PSTN, signals transmitted to orreceived from any one station (e.g., a server) can be directed to orreceived from a variety of other stations or servers within the network.Therefore, in a prepaid calling card scenario, whether or not thesignaling agent is located along the media path flow, the signalingagent can effectively control call setup, the duration of the call basedon the subscriber's account balance, and call tear down by directingsignaling messages to the appropriate media agent or other routingstation.

In the case of using an Internet protocol (IP) network system to place anon-prepaid call, with reference to FIG. 1, there is shown an IP networksystem designated generally by reference numeral 10 having a pluralityof media agents, i.e., devices for handling packets through the system10. In the IP network system 10, call media streams are routed from atelephone 20 through a PSTN telephone switch 30 to an IP telephonyswitch 40 over an ISDN line. The call media streams are then routed tothe IP network 50 over an IP line, and then over a corresponding IP lineto a destination IP telephony switch 40′, further to a destination PSTNtelephone switch 30′ over an ISDN line and finally to a destinationtelephone 20′. The call media streams can also be routed from thetelephone 20 to an IP terminal 75, such as a personal computer (PC).

The IP telephony switches 40 and 40′ provide basic interfacing betweenthe PSTN telephone switches 30 and 30′ and IP network 50 and includeboth gateways 60 a and 60 b, as well as gatekeepers 70 a and 70 b.Gatekeepers 70 a and 70 b use the signaling information provided by thegateways 60 a and 60 b to provide directory services. During a callsetup, the originating gatekeeper 70 a sets up a communication pathbetween the originating and terminating gateways 60 a, 60 b bydetermining the destination gatekeeper 70 b associated with adestination IP address or telephone number. The destination gatekeeper70 b selects a destination gateway 60 b to complete the IP virtualcircuit.

With reference to FIG. 2, an example of a call which originates in thePSTN, traverses the IP network, and terminates back in the PSTN isshown. First, at A, an Internet telephony service subscriber dials anaccess number provided by the Internet Telephony Service Provider. At B,the call is routed by the PSTN telephone switch 30 to the IP telephonyswitch 40. The gateway 60 a at C plays an announcement requesting thatthe subscriber enter the destination telephone number to be called. Thedestination digit information is sent to the gatekeeper 70 a.Accordingly, the gatekeeper 70 a determines a destination gatekeeper IPaddress based on the destination digit information. An IP packetrequesting the availability status of the destination gateway 60 b issent to the destination gatekeeper 70 b at D. The destination gatekeeper70 b responds to the request by providing destination gateway 60 bavailability and IP address information. The originating gatekeeper 70 athen transfers this information to the originating gateway 60 a at E.

With continued reference to FIG. 2, at F, the originating gateway 60 asets up a virtual circuit to the destination gateway 60 b. This circuitis identified by a call reference variable (CRV) that will be used byboth gateways 60 a, 60 b for the duration of the call to identify all IPpackets associated with this particular call. Finally, at G, thedestination gateway 60 b selects an outgoing PSTN voice trunk andsignals to the PSTN switch 30 to attempt to set up a call to the dialedtelephone number.

During the call, the packet-switched IP network 50 routes the IP packetsassociated with the particular call along different routes beforereaching the IP telephony switch 40′ or terminal 25 (e.g., a multimediapersonal computer (PC) equipped with Session Initiation Protocol (SIP)or H.323 software, a microphone and speakers). SIP and H.323 terminalssupport the encoding/decoding and packetization/sequencing ofinformation exchanged with other SIP and H.323 terminals or gateways.Packets are routed to the destination IP address contained within theheader of each packet and may travel over separate network paths beforearriving at their final destination for reassembly and resequencing.Accordingly, the routing of packets within the IP network is differentthan the routing of the call media streams by the PSTN during aconventional PSTN call, where all the call media streams associated witha particular call are routed along the same media path.

Accordingly, prepaid telephony services cannot be achieved via the IPnetwork shown by FIGS. 1 and 2 and described above, since call signalingmessages from a signaling agent, such as a server, do not take the samemedia path as the call media streams, since the IP network is apacket-based network where each packet from a particular station isrouted along a different media path than other packets. Further, withconventional servers and IP network hardware, the call signalingmessages cannot be directed or controlled to take the same path as thecall media streams.

Therefore, a need exists for a method of having a signaling agentcontrol at least one media agent of an IP network system for allowingand blocking call media streams from traversing through the media agent.

Further, a need exists for a method of directing all signaling messagestransmitted by a signaling agent and all media packets transmittingvoice and data communications through an IP network system through onemedia flow path.

SUMMARY OF THE INVENTION

The present invention provides methods for providing prepaid telephonyservice via an Internet protocol (IP) network system. A first methodprovides controlling at least one media agent or call routingstation/switch of an IP network system for allowing and/or blocking callmedia streams from traversing through the media agent. A second methodprovides directing all signaling messages transmitted by a signalingagent or station and all media packets transmitting voice and datacommunications through at least one common device within the IP networksystem.

The first method of the present invention enables prepaid telephonyservice via an IP network system and includes the steps of providing asignaling station between a PSTN telephone switch and an IP telephonyswitch of the IP network system; forwarding a telephone number enteredby a subscriber and received by the PSTN telephone switch to thesignaling station; determining if the telephone number matches a prepaidaccess telephone number stored within a database; forwarding thetelephone number to the IP telephony switch if the telephone number doesnot match the prepaid access telephone number to setup a non-prepaidcall via an IP network; transmitting prepaid access instructions fromthe signaling station to the subscriber if the telephone number matchesthe prepaid access telephone number to inform the subscriber to continueplacing a prepaid call by dialing at least a destination telephonenumber; forwarding the destination telephone number to the IP telephonyswitch via the PSTN telephone switch and signaling station; and settingup the prepaid call to the destination telephone number.

The method further includes the steps of during the prepaid call,continuously monitoring at the signaling station an account balancecorresponding to the subscriber; transmitting from the signaling stationto one of the PSTN telephone switch and the IP telephony switch a callinterrupt signal if the account balance is less than a predeterminedamount; receiving at one of the PSTN telephone switch and the IPtelephony switch the call interrupt signal and terminating the prepaidcall to the destination telephone number. It is contemplated that amessage be transmitted to the subscriber indicating an amount of callingtime available which corresponds to the account balance at least onetime prior to the signaling station transmitting the call interruptsignal.

Further, it is contemplated that the steps of determining if thetelephone number matches the prepaid access telephone number storedwithin the database of the signaling station, transmitting prepaidaccess instructions from the signaling station to the subscriber, andcontinuously monitoring at the signaling station the account balancecorresponding to the subscriber be performed by the IP telephony switchby programming the IP telephony switch accordingly.

Additionally, the method further includes the step of periodicallybilling the subscriber if the prepaid call was charged to a telephonenumber corresponding to the subscriber.

The second method of the present invention enables prepaid telephonyservice via an IP network system and includes the steps of forwarding atelephone number entered by a subscriber and received by a PSTNtelephone switch to an IP telephony switch; determining if the telephonenumber matches a prepaid access telephone number stored within adatabase; setting up a non-prepaid call via an IP network if thetelephone number does not match the prepaid access telephone number;transmitting prepaid access instructions from the IP telephony switch tothe subscriber if the telephone number matches the prepaid accesstelephone number to inform the subscriber to continue placing a prepaidcall by dialing at least a destination telephone number; forwarding thedestination telephone number to the IP telephony switch via the PSTNtelephone switch; setting up the prepaid call to the destinationtelephone number by setting up a virtual media path flow circuit betweenthe IP telephony switch, a relay station and one of a destination IPtelephony switch and an IP terminal, where the relay station is locatedwithin the IP network; and during the prepaid call, directing signalingmessages transmitted by the IP telephony switch, the destination IPtelephony and the IP terminal, and packets corresponding to the prepaidcall through the relay station.

The method further includes the steps of during the prepaid call,continuously monitoring, preferably, at the IP telephony switch or thedestination IP telephony switch, an account balance corresponding to thesubscriber; transmitting from the IP telephony switch, the destinationIP telephony switch or the IP terminal to the relay station a callinterrupt signal if the account balance is less than a predeterminedamount; receiving at the relay station the call interrupt signal andterminating the prepaid call. It is contemplated that a message betransmitted to the subscriber indicating an amount of calling timeavailable which corresponds to the account balance at least one timeprior to transmitting the call interrupt signal to the relay stationfrom the IP telephony switch, the destination IP telephony switch or theIP terminal. Further, it is contemplated that the step of continuouslymonitoring the account balance corresponding to the subscriber beperformed by a signaling station connected to the IP telephony switch orthe destination IP telephony switch by programming the signaling stationaccordingly.

Additionally, the method further includes the step of periodicallybilling the subscriber if the prepaid call was charged to a telephonenumber corresponding to the subscriber.

BRIEF DESCRIPTION OF THE DRAWINGS

Various preferred embodiments are described herein with references tothe drawings:

FIG. 1 is a block diagram of a prior art IP network system for placing acall via an IP network;

FIG. 2 is a prior art process flow block diagram for the IP networksystem of FIG. 1 indicating a sequence of events for placing a call viathe IP network;

FIG. 3 is a block diagram of an IP network system in accordance with afirst preferred method of the present invention for placing a prepaidcall via the IP network;

FIG. 4A is a flow chart for placing either a non-prepaid or a prepaidcall via the IP network according to the first preferred method;

FIG. 4B is a flow chart for continuously monitoring an account balancecorresponding to the subscriber during the prepaid call;

FIG. 4C is a flow chart for performing billing functions for billing thesubscriber after termination of the prepaid call;

FIG. 5 is a block diagram of an IP network system in accordance with asecond preferred method of the present invention for placing a prepaidcall via the IP network;

FIG. 6A is a flow chart for placing either a non-prepaid or a prepaidcall via the IP network according to the second preferred method; and

FIG. 6B is a flow chart for continuously monitoring an account balancecorresponding to the subscriber during the prepaid call.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention provides methods which enable prepaid telephonyservice between two subscribers of a Public Switched Telephone Network(PSTN), a subscriber of the PSTN and an IP multimedia terminal, or twoIP multimedia terminals via an Internet protocol (IP) network. A firstmethod provides controlling at least one media agent or call routingstation/switch of an IP network system for allowing and/or blocking callmedia streams from traversing through the media agent. A second methodprovides directing all signaling messages transmitted by a signalingagent or station and all media packets transmitting voice and datacommunications through at least one common device within the IP networksystem.

Referring now in detail to the drawings, in which like referencenumerals represent similar or identical elements throughout the severalviews, and with particular reference to FIG. 3, there is shown a blockdiagram of an IP network system designated generally by referencenumeral 300 for placing a prepaid call via an IP network 302 inaccordance with a first method of the present invention. The IP networksystem 300 includes a plurality of media agents, i.e., devices forhandling packets through the system 300, including a signaling station304. In the IP network system 300, call media streams are routed from atelephone 306 to a PSTN telephone switch 308 to the signaling station304 over an ISDN line to an IP telephony switch 310 over an IP line tothe IP network 302 over an IP line. The call media streams are thenrouted to a destination IP telephony switch 312 over an IP line to adestination PSTN telephone switch 314 over an ISDN line, and finally toa destination telephone 316. The call media streams can also be routedto an IP terminal 317, such as a PC.

The IP telephony switches 310, 312 provide basic interfacing between thePSTN telephone switches 308, 314 and IP network 302 and include bothgateways 318 and gatekeepers 320. It is apparent to persons skilled inthe art that signaling proxy servers, especially Session InitiationProtocol (SIP) proxy servers, could be used instead of gatekeepers 320.Gatekeepers 320 use the signaling information provided by the gateways318 to provide directory services. During a call setup, the originatinggatekeeper 320 a sets up a communication path between the originatingand terminating gateways 318 a, 318 b by determining the destinationgatekeeper 320 b associated with a destination IP address or telephonenumber. The destination gatekeeper 320 b selects a destination gateway318 b to complete the IP virtual circuit.

FIGS. 4A-C depict flow charts for placing the prepaid call via the IPnetwork according to the first preferred method. With reference to FIG.4A, a call is setup by entering a telephone number at step 400. Thetelephone number is then received by the PSTN telephone switch 308 andis routed to the signaling station 304 at step 401. The signalingstation 304 at step 402 determines if the telephone number matches aprepaid access telephone number stored within a database. The databaseis preferably stored within the signaling station 304 or a remotestation connected to the signaling station 304. If the telephone numberdoes not match the prepaid access telephone number, the telephone numberis forwarded to the IP telephony switch 310 at step 404 to setup anon-prepaid call via the IP network 302 at step 405, as described abovewith respect to placing a call using the originating and destinationgateways 318 a, 318 b and the originating and destination gatekeepers320 a, 320 b.

If the telephone number matches the prepaid access telephone number atstep 402, prepaid access instructions are transmitted from the signalingstation 304 to the subscriber at step 406 to inform the subscriber toplace a prepaid call by dialing at least a destination telephone number.Additional information to be dialed includes the subscriber's accountnumber and account personal identification number (PIN). If the accountinformation is determined to be accurate and a subscriber's accountbalance is sufficient (i.e., greater than a predetermined amount) asdetermined at step 407 by the signaling station 304, the destinationtelephone number is then forwarded at step 408 to the IP telephonyswitch 310 via the PSTN telephone switch 308 and signaling station 304.The prepaid call is then setup at step 409. If the account informationis not accurate or the subscriber's account balance is not sufficient,then the call is terminated.

With reference to FIG. 4B, the method further includes continuouslymonitoring during the prepaid call the account balance corresponding tothe subscriber at step 410. Preferably, step 410 is performed at thesignaling station 304. If the account balance is less than apredetermined amount, a call interrupt signal is transmitted from thesignaling station 304 to either the PSTN telephone switch 308 or the IPtelephony switch 310 at step 412. It is also contemplated that the callinterrupt signal is transmitted from the signaling station 304 to thePSTN telephone switch 314 or the IP telephony switch 312 at thedestination side, or to the IP terminal 317 in the case of telephonyservice between a PSTN subscriber and the IP terminal 317.

The call interrupt signal is then received by the PSTN telephone switch308 or the IP telephony switch 310 and the prepaid call to thedestination telephone number is terminated at step 414. It iscontemplated that a message be transmitted to the subscriber from thesignaling station 304, which indicates an amount of calling timeavailable according to the account balance, at least one time before thecall interrupt signal is transmitted by the signaling station 304.

Further, it is contemplated that the steps of determining if thetelephone number matches the prepaid access telephone number storedwithin the database of the signaling station, transmitting calling cardaccess instructions from the signaling station 304 to the subscriber,determining if the account information is accurate and that thesubscriber's account balance is sufficient, and continuously monitoringat the signaling station 304 the account balance corresponding to thesubscriber be performed by the IP telephony switch 310 by programmingthe IP telephony switch 310 accordingly to perform these steps.

Additionally, with reference to FIG. 4C, the method of the presentinvention further includes determining at the signaling station 304whether the prepaid call was charged to a particular telephone number atstep 416. If the prepaid call was charged to a particular telephonenumber, then the signaling station 304 at step 418 stores the chargesincurred and other information, such as a length of time of the prepaidcall and the destination telephone number, for billing the subscriber ata later time.

If the prepaid call was not charged to a particular telephone number,e.g., the prepaid call was a prepaid calling card call, then thesignaling station 304 at step 420 debits the subscriber's accountbalance and at step 422 stores the debited account balance in thedatabase.

It is contemplated that the billing steps of 416, 418, 420 and 422 beperformed by the IP telephony switch 310 by programming the IP telephonyswitch 310 accordingly. Hence, it is further contemplated that the IPtelephony switch 310 transmits the billing information to a plurality ofother IP telephony switches connected to the IP network. Therefore, if adifferent IP telephony switch is used to initiate a prepaid call in thefuture via the IP network 302, it contains the subscriber's billinginformation, including the subscriber's account balance.

With reference to FIG. 5, there is shown a block diagram of an IPnetwork system designated generally by reference numeral 500 for placinga prepaid call via an IP network in accordance with a second method ofthe present invention. The IP network system 500 includes a plurality ofmedia agents including a relay station 502 within an IP network 504. Inthe IP network system 500, call media streams are routed from atelephone 506 to a PSTN telephone switch 508 to an IP telephony switch510 and to the IP network 504. The call media streams are then routedover an IP line from the relay station 502 within the IP network 504 toa destination IP telephony switch 512 over an IP line and then to adestination PSTN telephone switch 514 over an ISDN line, and finally toa destination telephone 516. The call media streams can also be routedto an IP terminal 517.

As described above for the IP network system 300 shown in FIG. 3, the IPtelephony switches 510, 512 provide basic interfacing between the PSTNtelephone switches 508, 514 and IP network 504 and include both gateways518 and gatekeepers 520 which operate as described above.

FIGS. 6A-B depict flow charts for placing the prepaid call via the IPnetwork according to the second preferred method. With reference to FIG.6A, a call is setup by entering a telephone number at step 600. Thetelephone number is then received by the PSTN telephone switch 508 andis routed to the IP telephony switch 510 at step 601. The IP telephonyswitch 510 at step 602 determines if the telephone number matches aprepaid access telephone number stored within a database. The databaseis preferably stored within the IP telephony switch 510 or a remotestation connected to the IP telephony switch 510. If the telephonenumber does not match the prepaid access telephone number, the IPtelephony switch 510 at step 604 set ups a non-prepaid call via the IPnetwork 504, as described above with respect to FIG. 3, by placing acall using the originating and destination gateways 518 a, 518 b and theoriginating and destination gatekeepers 520 a, 520 b.

If the telephone number matches the prepaid access telephone number atstep 602, prepaid access instructions are transmitted to the subscriberat step 606 to inform the subscriber to place a prepaid call by dialingat least a destination telephone number. Additional information to bedialed includes the subscriber's account number and account personalidentification number (PIN). If the account information is determined tobe accurate and a subscriber's account balance is sufficient (i.e.,greater than a predetermined amount) as determined at step 607, thedestination telephone number is then forwarded at step 608 to the IPtelephony switch 510 via the PSTN telephone switch 508. The prepaid callis then setup at step 609 by setting up a virtual media path flowcircuit between the IP telephony switch 510, the relay station 502 andthe destination IP telephony switch 512 or the IP terminal 517. If theaccount information is not accurate or the subscriber's account balanceis not sufficient, then the call is terminated.

During the prepaid call, signaling and other messages transmitted by theIP telephony switch 510 are directed through the relay station 502 asindicated by step 610. Further, all media packets corresponding to theprepaid call are also directed through the relay station 502 asindicated by step 611.

The signaling messages and media packets are directed through the relaystation 502, by providing the IP address of the relay station 502 withina header of each message and media packet transmitted from the IPtelephony switch 510 and IP telephony switch 512, as well as the IPaddress of the IP telephony switch 512. Therefore, even though thepackets travel over separate network paths within the IP network 504before arriving at the IP telephony switch 512, the IP telephony switch510 or the IP terminal 517 for reassembly and resequencing, each packetpasses through the relay station 502 of the virtual media path flowcircuit.

With reference to FIG. 6B, the method further includes continuouslymonitoring during the prepaid call the account balance corresponding tothe subscriber at step 612. Preferably, step 612 is performed at the IPtelephony switch 510 or a remote station connected to the IP telephonyswitch 510. If the account balance is less than a predetermined amount,a call interrupt signal in the form of a packet is transmitted from theIP telephony switch 510 to the relay station 502 at step 614. It iscontemplated that the call interrupt packet can also be transmitted fromthe IP telephony switch 512 or the IP terminal 517. The call interruptpacket includes within a header the IP address of the relay station 502.The call interrupt signal is then received by the relay station 502 andthe prepaid call to the destination telephone number is then terminatedat step 616. The prepaid call is terminated by the relay stationblocking signaling and media packets from passing therethrough andreaching the IP telephony switch 512 or the IP terminal 517.

It is contemplated that a message be transmitted to the subscriberindicating an amount of calling time available which corresponds to theaccount balance at least one time prior to transmitting the callinterrupt signal to the relay station 502. Further, it is contemplatedthat the step of continuously monitoring the account balancecorresponding to the subscriber be performed by a signaling stationconnected to the IP telephony switch 510 by programming the signalingstation accordingly.

Additionally, the method of the present invention further includesdetermining whether the prepaid call was charged to a particulartelephone number. If the prepaid call was charged to a particulartelephone number, then the charges incurred and other information, suchas a length of time of the prepaid call and the destination telephonenumber, are stored for billing the subscriber at a later time. Thesesteps are preferably performed by the IP telephony switch 510 or aremote station connected to the IP telephony switch 510 and areidentical to steps 416 and 418 of FIG. 4C.

If the prepaid call was not charged to a particular telephone number,e.g., the prepaid call was a prepaid calling card call, then thesubscriber's account balance is debited and the debited account balanceis stored within the database. These steps are preferably performed bythe IP telephony switch 510 or a remote station connected to the IPtelephony switch 510 and are identical to steps 420 and 422 of FIG. 4C.

What has been described herein is merely illustrative of the applicationof the principles of the present invention. For example, the functionsdescribed above and implemented as the best mode for operating thepresent invention are for illustration purposes only. Other arrangementsand methods may be implemented by those skilled in the art withoutdeparting from the scope and spirit of this invention.

1. A system for providing prepaid telephony service, the systemcomprising: a packetized voice switch configured to determine whether atelephone number, supplied to establish a prepaid call and received viaa Public Switched Telephone Network (PSTN) telephone switch, matches aprepaid access telephone number; and a relay station coupled to thepacketized voice switch, wherein the relay station is configured as amedia agent to terminate the prepaid call if a match is determined, bycommunicating call media streams associated with the prepaid call to adata network terminal.
 2. A system according to claim 1, wherein thepacketized voice switch is further configured to determine whetheraccount information associated with the prepaid access telephone numberis accurate, wherein the call is terminated only if the accountinformation is accurate.
 3. A system according to claim 1, wherein thepacketized voice switch is further configured to monitor, during theprepaid call, an account balance associated with the prepaid accesstelephone number, and to interrupt the prepaid call if the accountbalance is less than a predetermined amount.
 4. A system according toclaim 3, wherein the prepaid account balance corresponds to asubscriber, the subscriber being notified about an available callingtime based on the account balance prior to interrupting the prepaidcall.
 5. A system according to claim 1, wherein, if the telephone numberdoes not match the prepaid access telephone number, a non-prepaid callis established by the packetized voice switch.
 6. A system according toclaim 1, wherein the relay station, in terminating the prepaid call,selectively blocks signaling and media packets generated by thepacketized voice switch from reaching a destination packetized voiceswitch.
 7. A system according to claim 1, wherein the data networkterminal is an Internet Protocol (IP) terminal.
 8. A method forproviding prepaid telephony service, the method comprising: determining,by a packetized voice switch, whether a telephone number, supplied toestablish a prepaid call and received via a Public Switched TelephoneNetwork (PSTN) telephone switch, matches a prepaid access telephonenumber, wherein the prepaid call is terminated, via a relay station, ifa match is determined, by communicating call media streams associatedwith the prepaid call to a data network terminal.
 9. A method accordingto claim 8, further comprising: determining, by the packetized voiceswitch, whether account information associated with the prepaid accesstelephone number is accurate, wherein the call is terminated only if theaccount information is accurate.
 10. A method according to claim 8,further comprising: monitoring, by the packetized voice switch, duringthe prepaid call, an account balance associated with the prepaid accesstelephone number, and to interrupt the prepaid call if the accountbalance is less than a predetermined amount.
 11. A method according toclaim 10, wherein the prepaid account balance corresponds to asubscriber, the subscriber being notified about an available callingtime based on the account balance prior to interrupting the prepaidcall.
 12. A method according to claim 8, wherein, if the telephonenumber does not match the prepaid access telephone number, a non-prepaidcall is established by the packetized voice switch.
 13. A methodaccording to claim 8, wherein the relay station, in terminating theprepaid call, selectively blocks signaling and media packets generatedby the packetized voice switch from reaching a destination packetizedvoice switch.
 14. A method according to claim 8, wherein the datanetwork terminal is an Internet Protocol (IP) terminal.